4.3 cruiser rough running

[Clarko1988]

87 4.3 merc back fires through carb at 8 btdc and runs great at 12btdc also when i turn the engine off i can hear air sucking threw motor. I am stumped.

 

[achris]

Check that the zero degree point is actually at zero degrees.

 

[Clarko1988]

Motor runs smooth other then when give it gas it back fires although when i rebuilt carb the kit came with a longer accelerator pump plunger could that have anything to do with it

 

[QBhoy]

I am sure you'll know already...but make sure its 100% fresh fuel you're giving her. Bad fuel will result in exactly the described too.

 

[Bondo]

Ayuh,..... The backfire says it's goin' Lean,.....